The PHP development group has officially released the latest alpha in the PHP 7.1.x series of releases. This is an alpha release and is not intended for production use.

The PHP development team announces the immediate availability of PHP 7.1.0 Alpha 2. This is the second alpha release for PHP 7.1.0. All users of PHP are encouraged to test this version carefully, and report any bugs and incompatibilities in the bug tracking system.

[...] For more information on the new features and other changes, you can read the NEWS file, or the UPGRADING file for a complete list of upgrading notes. These files can also be found in the release archive.

You can get this latest alpha release for testing on your own systems from the QA downloads page (for source) and the Windows QA site for the Windows binaries.